Thank you for this question. As long as your Track IR 4 camera is still working, there is no real reason to upgrade to Track IR 5. You can still use the latest Track IR 5 software with your Track IR 4 camera. You may download the latest version at the link listed below.

As you can see from the chart, TrackIR 5 features a huge upgrade in sensor sub-pixel resolution and field of view, which would eliminate the issues you are experiencing with the TIR4. In addition, you would get more effective range and LED power in the 5 which would help to overcome ambient sunlight in your playing space (which may or may not be affecting your 4).